Liquid crystal display apparatus having regions with different pretilt angles

ABSTRACT

The liquid crystal display apparatus of the invention includes a first substrate and a second substrate disposed so as to face each other, a liquid crystal layer sandwiched between the first substrate and the second substrate, a first alignment film formed between the liquid crystal layer and theist substrate, and a second alignment film formed between the liquid crystal layer and the second substrate. In the liquid crystal display apparatus, the liquid crystal layer includes a plurality of liquid crystal layer regions having aligning conditions which are different from each other, the plurality of liquid crystal layer regions including a first liquid crystal layer region and a second liquid crystal layer region, and wherein the orientation direction in a substrate plane of liquid crystal molecules in the vicinity of the center of the first liquid crystal layer region is different from the orientation direction in the substrate plane of liquid crystal molecules in the vicinity of the center of the second liquid crystal layer region, substantially by 90°.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display apparatus witha wide viewing angle and a method for producing the same.

2. Description of the Related Art

In a liquid crystal display (LCD), a liquid crystal layer includingliquid crystal molecules is provided between a pair of substrates. Whenthe orientation direction of the liquid crystal molecules is changed,the birefringence of the liquid crystal layer is also changed. Byutilizing the change in the refractive index, the LCD performs thedisplay. Accordingly, it is important that the liquid crystal moleculesare arranged as regularly as possible in the initial state. In order toregularly arrange the liquid crystal molecules in the initial state, thesurface conditions of the substrates which sandwich the liquid crystallayer should regulate the interactions between the liquid crystalmolecules and the surfaces.

In the method for performing such a regulation which is currently themost widely used, material for a liquid crystal alignment film isapplied to each of the surfaces of the substrates which face the liquidcrystal layer. The applied material is dried and cured, so as to formthe alignment film. Thereafter, the surface of the alignment film isrubbed. Thus, the liquid crystal molecules can be aligned in the rubbingdirection. The rubbing treatment is unidirectionally performed on theentire substrate, so that the liquid crystal molecules in the liquidcrystal layer which are in the vicinity of the substrate surface arealigned in one direction. In addition, the tilt angles (i.e., pretiltangles) of the liquid crystal molecules in the vicinity of the substratewith respect to the substrate surface are substantially equal to eachother.

In an LCD which uses thin film transistors (TFTs) as switching elements,i.e., in a TFT-LCD, the construction of a twisted nematic (TN) typeliquid crystal layer is adopted (an LCD of the TN mode). In such an LCDof the TN mode, the liquid crystal molecules between the pair ofsubstrates are continuously twisted by 90° along the directionperpendicular to the surfaces of the substrates, by means of thealignment films formed in the inward-facing surfaces of the substrates.

FIG. 18 is a plan view of an exemplary TN type LCD, and FIG. 19A shows across section of a picture element portion of the TN type LCD. The LCDis a TFT-LCD of an active matrix type. As is shown in FIG. 19A, a liquidcrystal layer 133 is sandwiched between substrates 131 and 132 which areprovided so as to face each other. The substrates 131 includes a glasssubstrate 131a on which scanning lines 112 and signal lines 113 areformed so as to cross each other as shown in FIG. 18. In the vicinity ofthe crossings of the scanning lines 112 and the signal lines 113, thinfilm transistors (TFTs) 120 as nonlinear switching elements are formed.In areas enclosed by the scanning lines 112 and the signal lines 113,pixel electrodes 110 are formed, respectively, in such a manner thatpart of each pixel electrode 110 and the scanning line 112 areoverlapped. The area 118 in which the pixel electrode 110 and thescanning line 112 are overlapped functions as an additional capacitance.Each of the TFTs 120 includes a gate electrode 115 which is branchedfrom a scanning line 112, a source electrode 116 which is branched froma signal line 113, and a drain electrode 117 for connecting the TFT 120to a pixel electrode 110. Over the glass substrate 131a on which theabove-mentioned elements are formed, an insulating protective film 131dand an alignment film 131e are formed in this order.

The other substrate 132 also has a glass substrate 132a on which a colorfilter 132b and a transparent electrode 132c are formed in this order.Over the glass substrate 132a on which the above-mentioned elements areformed, an insulating protective film (not shown) and an alignment film132e are formed in this order. The alignment film can also function asthe insulating protective film.

In the liquid crystal layer 133 sandwiched between the above-describedsubstrates 131 and 132, the liquid crystal molecules are aligned so thatthe orientation directions are continuously twisted by 90° along thedirection perpendicular to the surfaces of the substrates. A liquidcrystal molecule 133a near the center position along the directionperpendicular to the surfaces of the substrates has a predeterminedangle with respect to the substrate surface. The substrates 131 and 132are sealed at their ends by a resin or the like (not shown), and aperipheral circuit or the like for driving the liquid crystal isexternally mounted. LCDs which are of types other than the active matrixtype have the same construction as that described above.

In the TN type LCD, by the application of a voltage across thesubstrates 131 and 132, an electric field is generated in a directionperpendicular to the surfaces of the substrates 131 and 132. Inaccordance with the dielectric anisotropy of liquid crystal, the liquidcrystal molecules stand. By aligning the liquid crystal molecules inparallel to the direction of the electric field, the birefringence ofthe liquid crystal layer 133 is varied. If the direction of the electricfield is perpendicular to the direction to which the liquid crystalmolecules stand during no voltage application, that is, if the pretiltangle is 0, the direction to which the liquid crystal molecules stand isnot uniquely determined. As a result, a disclination line is generatedbetween liquid crystal domains having different standing directions inresponse to the electric field. Such a disclination line degrades thedisplay quality. Thus, in order to prevent the generation of thedisclination line, as shown in FIG. 19A, the liquid crystal moleculesare previously set to be tilted (i.e., to have a pretilt angle).

FIG. 19B shows the initial orientation of the liquid crystal when theliquid crystal panel shown in FIG. 19A is viewed from the side of thesubstrate 132 which is the upper one in FIG. 19A. Vector a in FIG. 19Bindicates the rubbing direction of the alignment film 132e, vector bindicates the rubbing direction of the alignment film 131e. The liquidcrystal molecules in the vicinity of each of the alignment films 131eand 132e are aligned along the respective rubbing direction (a or b inFIG. 19B) with a pretilt angle 6. The rubbing directions a and b formsan angle of 90° therebetween (the twist angle θt=90° in FIG. 19B). Theliquid crystal molecules in the liquid crystal layer 133 arecontinuously twisted by 90° along the thickness direction of the liquidcrystal layer 133. Accordingly, the liquid crystal molecule 133a nearthe middle position in the thickness direction of the liquid crystallayer 133 is also tilted by the angle δ with respect to the substrates131 and 132. The orientation direction of the liquid crystal molecule133a near the middle position is indicated by vector c in FIG. 19B. Thevector c divides the twist angle θt into two equal angles.

Herein, the plus side of the viewing angle θv in FIG. 19A (the sideindicated by θ1) is referred to as a positive viewing direction, and theminus side of the viewing angle θv in FIG. 19A (the side indicated byθ2) is referred to as a negative viewing direction. Specifically, thedirection in which the liquid crystal panel is viewed from the viewingpoint on the right side of the vertical broken line in FIG. 19B (i.e.,the line which is perpendicular to the orientation direction c of theliquid crystal molecule near the center position of the liquid crystallayer, and which divides the liquid crystal panel into two equal parts)is referred to as the positive viewing direction. The in-planeorientation direction of the liquid crystal panel of the liquid crystalmolecule 133a positioned near the center of the liquid crystal layer (cin FIG. 19B) is referred to as a reference orientation direction. As isseen from FIG. 19B, the reference orientation direction divides thetwist angle θt of the liquid crystal layer 133 into two equal angles.Also, the minus direction of c is referred to as a reference viewingdirection v. That is, the reference viewing direction v is therepresentative positive viewing direction.

Also herein, an imaginary clockface ( dial ) is drawn on the liquidcrystal panel, and the orientation direction of liquid crystal in theliquid crystal layer is indicated by the clock representation method.Specifically, in the construction in which the display on the liquidcrystal panel is actually viewed by a viewer, the upper side of theliquid crystal panel is represented as 12 o'clock, the lower sidethereof is represented as 6 o'clock. In a similar way, the orientationdirection of the liquid crystal layer is represented as the time in theimaginary clock indicated by the reference orientation direction of theliquid crystal layer in the liquid crystal panel. For example, theliquid crystal layer having the reference orientation direction c asshown in FIG. 19B is represented in such a manner as to "be oriented at3 o'clock" in the construction in which the front side of the figuresheet is regarded as the upper side of the liquid crystal panel.

The TN mode LCD, since the liquid crystal molecules are aligned in theabove-described manner, there occurs a phenomenon in which the contrastis different depending on the angle at which the LCD is viewed. Thereasons why the contrast changes will be described below.

FIG. 20 shows an exemplary applied voltages to transmittancecharacteristics in a normally white mode of an LCD in which light istransmitted during the no voltage application so as to perform a whitedisplay.

In FIG. 20, the solid line L1 shows the applied voltage to transmittancecharacteristic when the LCD shown in FIG. 19A is viewed in the directionperpendicular to the surfaces of the substrates (θv=0°). In this case,as the applied voltage value becomes high, the transmittance of light isdecreased. When the voltage value reaches a specific value, thetransmittance becomes substantially equal to zero. Accordingly, evenwhen a much higher voltage is applied, the transmittance remains atsubstantially zero.

When the viewing angle is inclined from the direction perpendicular tothe substrate face to the positive viewing direction, the appliedvoltage to transmittance characteristic is varied as is shown by solidline L2 in FIG. 20. Specifically, as the applied voltage becomes higher,the transmittance is decreased to some extent. When the applied voltageexceeds a specific value, the transmittance is increased. Then, thetransmittance is gradually decreased. Therefore, when the viewing angleis inclined in the positive viewing direction, there occurs a phenomenonin that the black and the white (the negative and positive) of the imageare inverted at a specific angle. This phenomenon occurs because theapparent birefringence of liquid crystal molecules having opticalanisotropy is varied depending on the viewing angle.

Referring to FIGS. 21A to 21C, the phenomenon will be described indetail. As is shown in FIG. 21A, when the applied voltage is zero or arelatively lower voltage, the center molecule 133a of the liquid crystallayer is observed in the form of an ellipse by the viewer 137 positionedin the positive viewing direction. As the applied voltage is graduallyincreased, the center molecule 133a is moved in such a manner that thelonger axis becomes aligned along the direction of the electric field,i.e., the direction perpendicular to the substrate face. Accordingly,the center molecule 133a is momentarily observed in the form of a circleby the viewer 137, as is shown in FIG. 21B. As the voltage is furtherincreased, the center molecule 133a becomes substantially in parallel tothe electric field direction. As a result, the center molecule 133a isobserved again in the form of an ellipse by the viewer 137, as is shownin FIG. 21C. In this way, the inversion phenomenon occurs.

If the viewing angle is tilted in the negative viewing direction, thevariation of the light transmittance with respect to the applied voltageis relatively small as compared with the case of being viewed from thedirection perpendicular to the substrates, as is shown by solid line L3in FIG. 20. As a result, when the LCD is viewed from the negativeviewing direction, the inversion phenomenon does not occur, but thecontrast is greatly degraded.

In the TN mode LCD, the inversion phenomenon when viewed from thepositive viewing direction and the degradation of contrast when viewedfrom the negative viewing direction cause serious problems for theviewer, and they result in doubts about the display properties of theLCD.

As to techniques for improving the inversion phenomenon, JAPAN DISPLAY'92, pages 591-594, and page 886 describe the following two methods. Inone method, the surface of the alignment film is unidirectionallyrubbed, and then a resist is deposited on a part of the alignment film.Then, the rubbing is performed to the portion which is not covered withthe resist in the direction reversed from the previous rubbingdirection. Thereafter, the resist is removed. As a result, one and thesame liquid crystal cell includes a different orientation direction ofliquid crystal molecules in the vicinity of the center of the liquidcrystal layer. In the other method, polyimide alignment films made ofdifferent compositions are juxtaposed and then they are subjected to therubbing treatment. As a result, a plurality of pretilt angles are formeddepending on the compositions thereof. According to these methods, twotypes of regions having opposite reference orientation directions areformed in one and the same cell, so that the viewer can mixedly observethe viewing characteristics in both directions. As a result, theinversion phenomenon when viewed from the positive viewing direction andthe significant reduction of the contrast when viewed from the negativeviewing direction are reduced and improved.

As described above, the viewing characteristics in the positive viewingdirection and in the negative viewing direction are made uniform, butthere exists another viewing characteristic in the directionperpendicular to the two reference orientation directions which areopposite to each other by 180° (i.e., in 6 o'clock or 12 o'clockdirection when the two reference orientation directions are regarded as3 o'clock and 9 o'clock direction ). The viewing characteristic in theperpendicular direction is different from the viewing characteristics inthe positive and negative viewing directions. The above methods cannotmake the entire viewing characteristics uniform. In the above-describedmethods, regions having different aligning conditions are formed on bothalignment films, so that it is necessary to align the boundary betweenthe regions having different aligning conditions on one substrate withthe boundary on the other substrate when the substrates are attached toeach other. However, it is extremely difficult to precisely align theboundaries with each other in the actual process. Thus, it is necessaryto form a light blocking film in view of the possible deviation of thealignment of boundaries. This causes the opening ratio to be decreased.

Display apparatuses have various applications, so it is desired that thescreen display can attain equal viewing characteristics for wide anglesin all viewing directions. There may be cases where equal viewingcharacteristics for wide angles are required in three directions (e.g.,at 3 o'clock, 6 o'clock, and 9 o'clock directions) or where equalviewing characteristics for wide angles are required in two directions(e.g., at 3 o'clock and 6 o'clock directions). Thus, it is desirablethat viewing characteristics required for the desired application can beobtained.

In another attempt to eliminate the inversion phenomenon when viewedfrom the positive viewing direction and the degradation of contrast whenviewed from the negative viewing direction, a rectangular region 119 asshown in FIG. 18 in which the orientation direction of the liquidcrystal molecule 133a in the vicinity of the center of the liquidcrystal layer 133 is different from that in the other region is formedin the picture element shown by a broken line in FIG. 18. In moredetail, two regions having reference orientation directions which aredifferent from each other by 180° are formed in one picture element, sothat the contrast degradation when viewed from the negative viewingdirection is compensated, and the inversion phenomenon when viewed fromthe positive viewing direction is suppressed.

However, in the case where one picture element has liquid crystal layerregions having different reference orientation directions formedtherein, as the time elapses, the aligning condition of one liquidcrystal layer region may be absorbed by the aligning condition of theother liquid crystal layer region. In addition, in the boundary areabetween the liquid crystal layer regions, a disclination line occurs.This causes the contrast to be degraded.

SUMMARY OF THE INVENTION

The liquid crystal display apparatus of this invention includes a firstsubstrate and a second substrate disposed to face each other; a liquidcrystal layer sandwiched between the first substrate and the secondsubstrate; and a first alignment film formed between the liquid crystallayer and the first substrate, and a second alignment film formedbetween the liquid crystal layer and the second substrate, wherein theliquid crystal layer includes a plurality of liquid crystal layerregions having aligning conditions which are different from each other,the plurality of liquid crystal layer regions including a first liquidcrystal layer region and a second liquid crystal layer region, andwherein an orientation direction in a substrate plane of liquid crystalmolecules in the vicinity of the center of the first liquid crystallayer region is different from an orientation direction in the substrateplane of liquid crystal molecules in the vicinity of the center of thesecond liquid crystal layer region, substantially by 90°.

In one embodiment of the invention, liquid crystal molecules in thesecond liquid crystal layer region are twisted in a direction oppositeto a direction in which liquid crystal molecules in the first liquidcrystal layer region are twisted.

In another embodiment of the invention, a surface condition of the firstalignment film is different from a surface condition of the secondalignment film in the first liquid crystal layer region, and a surfacecondition of the first alignment film is substantially the same as asurface condition of the second alignment film in the second liquidcrystal layer region.

In another embodiment of the invention, a pretilt angle of the firstalignment film is different from a pretilt angle of the second alignmentfilm in the first liquid crystal layer region, and a pretilt angle ofthe first alignment film is substantially the same as a pretilt angle ofthe second alignment film in the second liquid crystal layer region. Thepretilt angle of the first alignment film and the pretilt angle of thesecond alignment film in the first liquid crystal layer region may besmaller than 20°, and a difference between the pretilt angles of thefirst and the second alignment films in the first liquid crystal layerregion may be 1.5° or more.

In another embodiment of the invention, the plurality of liquid crystallayer regions further includes a third liquid crystal layer region, andan orientation direction in the substrate plane of liquid crystalmolecules in the vicinity of the center of the third liquid crystallayer region is different from the orientation direction in the firstliquid crystal layer region by 180°, and different from the orientationdirection in the second liquid crystal layer region by 90°. A pretiltangle of the first alignment film and a pretilt angle of the secondalignment film in the third liquid crystal layer region may be smallerthan 20°, and a difference between the pretilt angles of the first andthe second alignment films in the third liquid crystal layer region maybe 1.5° or more. The pretilt angle of the first alignment film may belarger than the pretilt angle of the second alignment film in the firstliquid crystal layer region, and the pretilt angle of the firstalignment film may be smaller than the pretilt angle of the secondalignment film in the third liquid crystal layer region. Alternatively,the pretilt angle of the first alignment film may be smaller than thepretilt angle of the second alignment film in the first liquid crystallayer region, and the pretilt angle of the first alignment film may belarger than the pretilt angle of the second alignment film in the thirdliquid crystal layer region.

In another embodiment of the invention, the second liquid crystal layerregion is formed between the first liquid crystal layer region and thethird liquid crystal layer region. The first, the second, and the thirdliquid crystal layer regions may have substantially equal areas.Alternatively, an area of the second liquid crystal layer region issmaller than an area of each of the first and the third liquid crystallayer regions.

In another embodiment of the invention, a surface condition of the firstalignment film in the first liquid crystal layer region is substantiallyequal to a surface condition of the first alignment film in the secondliquid crystal layer region, and a surface condition of the secondalignment film in the first liquid crystal layer region is differentfrom a surface condition of the second alignment film in the secondliquid crystal layer region. A pretilt angle of the first alignment filmmay have an intermediate value between a pretilt angle of the secondalignment film in the first liquid crystal layer region and a pretiltangle of the second alignment film in the second liquid crystal layerregion.

In another embodiment of the invention, a surface condition of the firstalignment film in the second liquid crystal layer region issubstantially equal to a surface condition of the first alignment filmin the first liquid crystal layer region, and a surface condition of thesecond alignment film in the second liquid crystal layer region issubstantially equal to a surface condition of the second alignment filmin the third liquid crystal layer region.

In another embodiment of the invention, the first alignment film hasequal surface conditions in all of the first, the second, and the thirdliquid crystal layer regions, and the second alignment film hasdifferent surface conditions among the first, the second, and the thirdliquid crystal layer regions.

In another embodiment of the invention, pretilt angles of the secondalignment film in the first, the second, and the third liquid crystallayer regions are different from each other.

In another embodiment of the invention, each of the plurality of liquidcrystal layer regions corresponds to one pixel region.

In another embodiment of the invention, the plurality of liquid crystallayer regions are formed in one pixel region.

In another embodiment of the invention, each of the plurality of liquidcrystal layer regions are continuously formed over a plurality of pixelregions.

In another embodiment of the invention, an orientation direction in thesubstrate plane of liquid crystal molecules which are in contact withone of the first alignment film and the second alignment film issubstantially parallel to a boundary between the plurality of liquidcrystal layer regions.

In another embodiment of the invention, the liquid crystal displayapparatus further includes a light blocking film located on the boundarybetween the plurality of liquid crystal layer regions.

In another embodiment of the invention, a nonlinear element is formed inthe pixel region, and the boundary is disposed at a position remotestfrom the nonlinear element.

In another embodiment of the invention, a nonlinear element is formed inthe pixel region, and the light blocking film is formed of an opaquematerial which constitutes the nonlinear element.

According to another aspect of the invention, a method for producing aliquid crystal display apparatus comprising a first substrate and asecond substrate disposed to face each other and liquid crystalsandwiched between the first substrate and the second substrate isprovided. The method includes: a step of forming a first alignment filmon the first substrate, and forming a second alignment film on thesecond substrate; a surface treatment step of forming a plurality ofportions having surface conditions which are different from each other,on at least one of the first alignment film and the second alignmentfilm; and an assembly step of attaching the first substrate to thesecond substrate, and injecting the liquid crystal between the firstsubstrate and the second substrate, so as to form a plurality of liquidcrystal layer regions having different orientation directions in asubstrate plane of liquid crystal molecules in the vicinity of thecenter of the liquid crystal along a thickness direction of the liquidcrystal between the first and the second substrates, wherein theplurality of liquid crystal layer regions includes a first liquidcrystal layer region and a second liquid crystal layer region, and anorientation direction in the substrate plane of liquid crystal moleculesin the vicinity of the center of the first liquid crystal layer regionis different from an orientation direction in the substrate plane ofliquid crystal molecules in the vicinity of a center of the secondliquid crystal layer region, substantially by 90°.

In one embodiment of the invention, the surface treatment step includesa step of forming a plurality of portions having different pretiltangles by partially changing the surface condition of at least one ofthe first and the second alignment films.

In another embodiment of the invention, the step of forming theplurality of portions having different pretilt angles includes a step ofselectively irradiating the at least one of the first and the secondalignment films with ultraviolet rays.

In another embodiment of the invention, the step of forming theplurality of portions having different pretilt angles includes a step ofbringing the at least one of the first and the second alignment filmsinto contact with one of an acid solution, an alkaline solution, andsolutions containing these as main components.

In another embodiment of the invention, the step of forming theplurality of portions having different pretilt angles includes a step ofirradiating the at least one of the first and the second alignment filmswith a plasma of a gas selected from a group consisting of O₂, Ar, andKr.

In another embodiment of the invention, the method further includes astep of forming an underlying film on each of the first and the secondsubstrates, prior to the step of forming the first and the secondalignment films, wherein the surface treatment step includes a step ofmaking a part of at least one of the underlying films having differentdegrees of roughness, and a step of forming the first and the secondalignment films on the underlying films, thereby changing a surfacecondition of at least one of the first and the second alignment films.

In another embodiment of the invention, the step of making differentdegrees of roughness includes a step of selectively irradiating theunderlying film with ultraviolet rays.

In another embodiment of the invention, the step of making differentdegrees of roughness includes a step of bringing the underlying filminto contact with one of an acid solution, an alkaline solution, andsolutions containing these as main components.

In another embodiment of the invention, the step of making differentdegrees or roughness includes a step of irradiating the underlying filmwith a plasma of a gas selected from a group consisting of O₂, Ar, andKr.

In another embodiment of the invention, the step of making differentdegrees of roughness includes a step of forming an insulating film on apredetermined area of a surface of the underlying film.

In another embodiment of the invention, the step of making differentdegrees of roughness includes a step of forming the different degrees ofroughness in at least one of the underlying films by photolithography.

In another embodiment of the invention, in the step of forming the firstand the second alignment films on the underlying films, a surfacecondition of at least one of the first and the second alignment films iscontrolled by changing a thickness of the at least one of the first andthe second alignment films.

In another embodiment of the invention, the plurality of liquid crystallayer regions further includes a third liquid crystal layer region, andan orientation direction in the substrate plane of liquid crystalmolecules in the vicinity of the center of the third liquid crystallayer region is different from the orientation direction in the firstliquid crystal layer region substantially by 180°, and different fromthe orientation direction in the second liquid crystal layer regionsubstantially by 90°.

In another embodiment of the invention, the first alignment filmincludes a first and a second portions having different pretilt angles,and the second alignment film includes a third and a fourth portionshaving different pretilt angles, and wherein the method further includesa step of positioning the first and the second substrates so that thesecond portion of the first alignment film is divided by a boundarybetween the third and the fourth portions of the second alignment film.

In another embodiment of the invention, in the assembly step, the firstand the second substrates are assembled so as to adapt to liquid crystalhaving a twisted property in a direction opposite to a direction inwhich the injected liquid crystal is twisted, whereby the twisteddirections in the plurality of liquid crystal layer regions aredifferent from each other.

In the liquid crystal display apparatus of the invention, the liquidcrystal layer has a plurality of regions having different orientationdirections of liquid crystal molecules in the vicinity of the center ofthe liquid crystal layer along the thickness direction thereof. In moredetail, in the liquid crystal display apparatus of the invention, thereexist both a liquid crystal layer region in which the aligning conditionof liquid crystal molecules in the vicinity of one substrate isdifferent from that in the vicinity of the other substrate, and a liquidcrystal layer region in which the aligning condition of liquid crystalmolecules in the vicinity of one substrate is the same as that in thevicinity of the other substrate. In another case, there is no liquidcrystal layer region in which the aligning condition of liquid crystalmolecules in the vicinity of one substrate is the same as that in thevicinity of the other substrate, but there only exists liquid crystallayer regions in which the aligning condition of liquid crystalmolecules in the vicinity of one substrate is different from that in thevicinity of the other substrate. The orientation direction of liquidcrystal molecules in the vicinity of the center of each liquid crystallayer region is regulated by a combination of the pretilt angles ofliquid crystal molecules which are in contact with the alignment films.The viewing characteristics in the two reference viewing directionswhich are opposite to each other by 180° are realized by a combinationof different pretilt angles between the substrates. The viewingcharacteristic in a reference viewing direction perpendicular to thesereference viewing directions is realized by a combination of equalpretilt angles. Since the liquid crystal display apparatus of thisinvention has the above-described construction, the viewingcharacteristics in two or three directions can be made uniform.

Between adjacent liquid crystal layer regions having different aligningconditions, a liquid crystal layer region having equal pretilt angles onthe pair of substrates is formed. The liquid crystal layer region havingequal pretilt angles on the pair of substrates has a smaller area thanthe liquid crystal layer region having different aligning conditions. Asthe result of the construction, at the boundary between the differentaligning conditions, there is no region in which the liquid crystalmolecules do not stand up. Thus, a disclination line is not generated.

In the liquid crystal display apparatus of the invention, the boundarybetween different aligning conditions on one substrate is disposed so asto divide one aligning condition on the other substrate. Thus, it isunnecessary to precisely align the boundaries with each other when thesubstrates are attached to each other during panel assembly. Therefore,it is unnecessary to form a black matrix in view of the misalignment atthe boundary, unlike the case in which the boundaries are aligned witheach other.

According to the invention, the boundaries between a plurality of liquidcrystal layer regions having different aligning conditions is formedcontinuously over at least two picture elements, so that the free energyincluded in the boundary is decreased. Thus, the absorption of onealigning condition to another aligning condition can be prevented.

The boundary between a plurality of liquid crystal layer regions havingdifferent orientation directions in one picture element is parallel tothe orientation direction of liquid crystal molecules which are incontact with one substrate, so that the disorder of the liquid crystalorientation is suppressed. As a result, the generation of a disclinationline can be suppressed.

If the boundary is covered with a light blocking film, the coveredportion does not contribute the display, irrespective of the generationof a disclination line.

If the light blocking film is formed of the same material as that forthe nonlinear element, additional processing is not required.

Thus, the invention described herein makes possible the advantages of(1) providing a liquid crystal display apparatus having a wide viewingangle with an improved display quality in which the viewing performancecan be effectively improved, and a method for producing the liquidcrystal display apparatus, and (2) providing a liquid crystal displayapparatus in which positive and negative viewing directions are readilyformed in one and the same cell and a method for producing the liquidcrystal display apparatus.

These and other advantages of the present invention will become apparentto those skilled in the art upon reading and understanding the followingdetailed description with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view showing a first example of an LCD ofthe invention.

FIG. 1B shows the relationship between the rubbing direction and thereference orientation direction in the LCD shown in FIG. 1A.

FIG. 2A is a cross-sectional view showing a second example of an LCD ofthe invention.

FIG. 2B shows the relationship between the rubbing direction and thereference orientation direction in the LCD shown in FIG. 2A.

FIG. 3A is a cross-sectional view showing a third example of an LCD ofthe invention.

FIG. 3B shows the relationship between the rubbing direction and thereference orientation direction in the LCD shown in FIG. 3A.

FIGS. 4 and 5 are cross-sectional views showing modifications of the LCDof the invention.

FIG. 6 is a cross-sectional view showing a sixth example of an LCD ofthe invention.

FIG. 7 is a cross-sectional view showing a seventh example of an LCD ofthe invention.

FIG. 8 is a plan view showing an eighth example of an LCD of theinvention.

FIG. 9 is a cross-sectional view of the LCD shown in FIG. 8.

FIG. 10 is a plan view showing a modification of the eighth example ofan LCD of the invention.

FIG. 11 is a plan view showing a ninth example of an LCD of theinvention.

FIG. 12 is a cross-sectional view of the LCD shown in FIG. 11.

FIG. 13 is a plan view showing a modification of the ninth example ofthe invention.

FIG. 14 is a plan view showing a modification of the ninth example ofthe invention.

FIG. 15 is a plan view showing a tenth example of an LCD of theinvention.

FIG. 16 is a cross-sectional view of the LCD shown in FIG. 15.

FIG. 17 is a plan view showing a modification of the tenth example ofthe invention.

FIG. 18 is a plan view showing a conventional LCD.

FIG. 19A is a cross-sectional view of the LCD shown in FIG. 18.

FIG. 19B shows the relationship between the orientation direction ofliquid crystal and the rubbing direction.

FIG. 20 shows the applied voltage to transmittance characteristics in aconventional normally white mode LCD.

FIGS. 21A, 2lB, and 21C are diagrams for illustrating the inversionphenomenon in an LCD.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described by way ofillustrative examples.

EXAMPLE 1

In Example 1, so as to form two liquid crystal layer regions withdifferent pretilt angles, portions having different pretilt angles areformed on one of the alignment films formed on the inwardly-facingsurfaces of a pair of substrates. FIG. 1A schematically shows thealigning conditions of liquid crystal molecules in an LCD of thisexample. Various switching elements and electric wirings, and the likeare not essential in this application, so that they are not shown inFIG. 1A. In this example, it is assumed that each of the liquid crystallayer regions indicated by (A) and (B) corresponds to one pixel region.

The LCD includes, as shown in FIG. 1A, a transparent base substrate 1and a transparent counter substrate 11 which is disposed so as to facethe base substrate 1. Over the entire surface of the base substrate 1, atransparent electrode 2 is formed. An alignment film 3 is formed overthe entire surface of the base substrate 1 so as to cover thetransparent electrode 2. Over the entire surface of the countersubstrate 11, a transparent electrode 12 is formed. An alignment film 13is formed over the entire surface of the counter substrate 11 so as tocover the transparent electrode 12. The alignment films 3 and 13 aresubjected to the aligning treatment (e.g., the rubbing treatment). Thebase substrate 1 and the counter substrate 11 are arranged in such aconstruction that the alignment films 3 and 13 face each other and theliquid crystal which will be sealed between the substrates 1 and 11should be left-handed 90° twisted. Then, into a gap between thesubstrates 1 and 11 having the above-described construction, liquidcrystal having a right-handed twist property is injected, so as to forma liquid crystal layer 4. The grades of inclination of liquid crystalmolecules 5 with respect to the surfaces of the alignment films 3 and 13in the vicinity of the interface between the liquid crystal layer 4 andthe alignment film 3 and the interface between the liquid crystal layer4 and the alignment film 13 correspond to pretilt angles δ of the liquidcrystal molecules 5.

In this example, on the side of the alignment film 3 formed on the basesubstrate 1, the pretilt angle ι of the liquid crystal molecules 5 inthe liquid crystal layer region (A) is smaller than that in the liquidcrystal layer region (B). On the side of the alignment film 13 formed onthe counter substrate 11, the pretilt angle δ in the liquid crystallayer region (A) is equal to that in the liquid crystal layer region(B). In addition, the pretilt angle δ on the side of the alignment film13 formed on the counter substrate 11 is set to be larger than that inthe liquid crystal layer region (A) on the side of the alignment film 3formed on the base substrate 1.

A method for producing the LCD is now described.

Transparent electrodes 2 and 12 of ITO or the like are formed on thebase substrate 1 and the counter substrate 11, respectively. Alignmentfilms 3 and 13 are formed so as to cover the transparent electrodes 2and 12 over the entire surfaces of the base substrate 1 and the countersubstrate 11, respectively. In this example, as a material of thealignment film, polyimide which makes the pretilt angle δ of liquidcrystal molecules 5 to be 5° is used. Polyimide films are formed on thesubstrates 1 and 11 on which the transparent electrodes 2 ad 12 areformed, by spin coating, printing, or other methods. Then, the surfaceof the formed polyimide film is rubbed. Instead of polyimide, thealignment film may be formed of an organic material such as polyamide,polystyrene, polyamideimide, epoxyacrylate, spiranacrylate,polyurethane, or the like.

Thereafter, the polyimide film 3 on the base substrate 1 is selectivelyirradiated with ultraviolet rays, so as to form two types of regions inwhich the pretilt angles ι of liquid crystal molecules in contact withthe regions are different from each other. Specifically, the portioncorresponding to the liquid crystal layer region (B) of the polyimidefilm 3 is covered with a resist, so that only the portion correspondingto the liquid crystal layer region (A) is irradiated with theultraviolet rays. As a result, the pretilt angle δ of the liquid crystalmolecules 5 which are in contact with the irradiated portion of thepolyimide film 3 becomes smaller than 5° in the portion which is notirradiated with the ultraviolet rays. In this example, the irradiationof ultraviolet rays is performed so that the pretilt angle δ of theliquid crystal molecules 5 in contact with the irradiated portion is setto be 3.5°. An area of the irradiated portion is made equal to that ofthe non-irradiated portion. To the polyimide film 13 on the countersubstrate 11, the irradiation of ultraviolet rays is not performed, sothat the pretilt angles δ are all set to be 5° on the side of thecounter substrate 11.

Finally, the substrates 1 and 11 having the above-described constructionare attached so as to face each other, and so as to correspond to theleft-handed twist liquid crystal. Then, the liquid crystal havingright-handed twist property is injected into the gap between thesubstrates 1 and 11. As a result, two liquid crystal layer regions,i.e., a liquid crystal layer region (A) in which the pretilt angle onthe counter substrate 11 side is 5° and the pretilt angle on the basesubstrate 1 side is 3.5° and a liquid crystal layer region (B) in whichthe pretilt angles on both sides are equal to 5° are formed.

FIG. 1B shows the relationship between the rubbing directions 3a and 13aon the alignment films 3 and 13 and reference orientation directions inthe respective liquid crystal layer regions. In the liquid crystal cellwhich is obtained in the above-described manner, the orientationdirections of liquid crystal molecules in the vicinity of the center ofthe liquid crystal layer 4 along the thickness direction thereof are setin the following manner. In the liquid crystal layer region (A) in whichthe pretilt angle δ on the counter substrate 11 side is larger, theliquid crystal is right-handed twisted, and the orientation direction ofthe liquid crystal molecules is substantially parallel to the substrateface in the vicinity of the center of the liquid crystal layer 4. Duringthe voltage application, the standing of the liquid crystal molecules inthe vicinity of the center is regulated by the alignment film 13 on thecounter substrate 11 having the larger pretilt angle δ. Accordingly, thein-plane orientation direction of the liquid crystal molecules in theliquid crystal panel, i.e., the reference orientation direction isindicated by c_(A) shown in FIG. 1A and 1B. In the liquid crystal layerregion (B) in which the pretilt angles δ on both sides are equal to eachother, although the liquid crystal has the right-handed twist property,the liquid crystal is regulated by the cell which is constructed so asto correspond to the left-handed twisted liquid crystal. As a result,the liquid crystal is left-handed twisted. Accordingly, during thevoltage application, in FIG. 1A, the front end of each liquid crystalmolecule 5 in the vicinity of the center points downwardly, and theother end thereof stands. Thus, the reference orientation direction ofthe liquid crystal layer region (B) is a direction c_(B) from the frontside of the figure sheet to the other side, as shown in FIGS. 1A and 1B.The direction c_(B) is different from the reference orientationdirection c_(A) in the liquid crystal layer region (A).

In this example, in the liquid crystal layer region (A), the differencebetween the pretilt angle on the counter substrate 11 side and thepretilt angle on the base substrate 1 side is set to be 1.5°. If thedifference between the pretilt angles is made smaller than 1.5°, a goodorientation regulation by the alignment film having the larger pretiltangle cannot be performed. The maximum value of the pretilt angle (i.e.,a pretilt angle obtained without the irradiation of ultraviolet rays)should be set smaller than 20°. If the pretilt angle is equal to orlarger than 20°, the orientation direction of liquid crystal moleculesin the vicinity of the center cannot be regulated by the alignment filmhaving the larger pretilt angle, even when the pretilt angle on onesubstrate side is set to be larger than that of the other substrateside, because the orientation regulating power by the cell structure isstronger than the orientation regulating power by the alignment filmhaving the larger pretilt angle.

In this example, the material of liquid crystal injected into the gapbetween the base substrate 1 and the counter substrate 11 and thecombinations of the substrates 1 and 11 which are subjected to thealigning treatment are selected so that the reference orientationdirection c_(A) in the liquid crystal layer region (A) is different fromthe reference orientation direction c_(B) in the liquid crystal layerregion (B) by 90°. The reference orientation directions in the tworegions are not necessarily selected from 3 o'clock, 6 o'clock, 9o'clock, and 12 o'clock directions. It is sufficient that the directionsare different from each other by 90°. For example, they are selected asa direction indicating 4:30 and a direction indicating 7:30. Asdescribed above, according to this example, two types of liquid crystallayer regions having different reference orientation directions by 90°are formed so as to have equal areas. Accordingly, the viewingcharacteristics viewed in the reference viewing directions which aredifferent from each other by 90° are mixed at the ratio of 1:1, so thatgood viewing performance can be obtained.

In this example, each of the liquid crystal layer regions (A) and (B)corresponds to one pixel region. Alternatively, if one pixel region isdivided into two sub-regions which correspond to the liquid crystallayer regions (A) and (B), respectively, two different referenceorientation directions are formed in one pixel region. Accordingly, afiner image can be realized.

In the LCD of Example 1, the aligning condition on the counter substrate11 side is entirely uniform, and two types of portions having differentaligning conditions are provided on the base substrate 1 side.Accordingly, the liquid crystal layer 4 is divided into two types ofregions having different reference orientation directions, by theboundary between the portions having different aligning conditions.Therefore, unlike the prior art in which regions having referenceorientation directions different from each other by 180° are formed, itis unnecessary to align the boundary between the portions havingdifferent aligning conditions on the counter substrate side with theboundary between the portions having different aligning conditions onthe base substrate side when the substrates are attached to each other.As a result, it is unnecessary to form a black matrix which was formedin view of the possible misalignment in the prior art requiring thealignment of boundaries. Therefore, the opening ratio cannot be reduced.

EXAMPLE 2

In an LCD of Example 2, three types of liquid crystal layer regionshaving different reference orientation directions are formed. FIG. 2Ashows a cross section of the LCD of this example. In this example, twotypes of portions having different aligning conditions are formed on thealignment film 3 on the base substrate 1, and also two types of portionshaving different aligning conditions are formed on the alignment film 13on the counter substrate 11. By the combinations of the aligningconditions of the substrates 1 and 11, three types of liquid crystallayer regions (A), (B), and (C) having different reference orientationdirections are formed. In this example, it is assumed that each of theliquid crystal layer regions (A), (B), and (C) corresponds to one pixelregion.

Transparent electrodes 2 and 12 are formed on the base substrate 1 andthe counter substrate 11, respectively. Polyimide films are formed so asto cover the transparent electrodes 2 and 12 over the entire surfaces ofthe base substrate 1 and the counter substrate 11, respectively. Thepolyimide films are rubbed, so as to obtain alignment films 3 and 13.Thereafter, the alignment film 3 and 13 are partially covered with aresist, and then irradiated with ultraviolet rays. In this example, inboth alignment films, the area of the portion which is covered with theresist is set to be twice as large as the area of the portion which isirradiated with ultraviolet rays without the resist. As a result, bothin the alignment film 3 on the base substrate 1 and in the alignmentfilm 13 on the counter substrate 11, two types of portions havingdifferent aligning conditions are formed. In this example, the samepolyimide film as that used in Example 1 is used as the alignment film,so that the pretilt angle δ of liquid crystal molecules which are incontact with the portion which is not irradiated with ultraviolet raysof the polyimide film is 5°. In this example, the irradiation ofultraviolet rays is performed so that the pretilt angle of the liquidcrystal molecules in contact with the irradiated portion is set to be3.5°.

The substrates 1 and 11 having the above-described construction areattached so that the rubbing directions for the substrates 1 and 11 willcorrespond to the left-handed twisted liquid crystal and so that theboundary between portions having different aligning conditions on onesubstrate divides the portion which is not irradiated with ultravioletrays (the portion having the larger pretilt angle) on the othersubstrate into two substantially equal parts. Also, the substrates 1 and11 are attached to each other so as to set the faces on which thealignment films are formed inwardly. Finally, liquid crystal havingright-handed twist property is injected into the gap between thesubstrates 1 and 11. As a result, a liquid crystal layer region (A) inwhich the pretilt angle on the counter substrate 11 side is smaller thanthat on the base substrate 1 side, a liquid crystal layer region (B) inwhich the pretilt angles on both sides are equal, and a liquid crystallayer region (C) in which the pretilt angle on the counter substrate 11side is larger than that on the base substrate 1 side are formed.

FIG. 2B shows the relationships between the rubbing directions 3a and13a on the alignment films 3 and 13 and reference orientation directionsin the respective liquid crystal layer regions. In the liquid crystalcell which is obtained in the above-described manner, the orientationdirections of liquid crystal molecules in the vicinity of the center ofthe liquid crystal layer 4 along the thickness direction thereof are setin the following manner. In the liquid crystal layer region (A), sincethe pretilt angle on the base substrate 1 side is larger than that onthe counter substrate 11 side, the liquid crystal is right-handedtwisted, and the orientation direction of the liquid crystal moleculesis substantially parallel to the substrate face in the vicinity of thecenter of the liquid crystal layer. The in-plane orientation directionof the liquid crystal molecules in the liquid crystal panel in thevicinity of the center in the region (A) is a direction indicated byc_(A) shown in FIGS. 2A and 2B. In the liquid crystal layer region (B)in which the pretilt angles on both sides are equal to each other,although the liquid crystal has the right-handed twist property, theliquid crystal is regulated by the cell, so as to correspond to theleft-handed twisted liquid crystal. As a result, the liquid crystal isleft-handed twisted. Accordingly, the reference orientation direction inthe liquid crystal layer region (B) is the direction c_(B) from thefront side of the figure sheet to the other side, as shown in FIGS. 2Aand 2B. In the liquid crystal layer region (C), since the pretilt angleon the counter substrate 11 side is larger than that on the basesubstrate 1 side, the liquid crystal is right-handed twisted, as in theliquid crystal layer region (A). However, the relationship of themagnitude between the pretilt angles on the substrates 1 and 11 in theliquid crystal layer region (C) is reversed from that in the liquidcrystal layer region (A), so that the reference orientation directionc_(C) in the liquid crystal layer region (C) is different from thereference orientation direction c_(A) in the liquid crystal layer region(A), by 180°. In this example, the material of liquid crystal and thecombinations of the substrates 1 and 11 which are subjected to thealigning treatment are selected so that the reference orientationdirection c_(B) in the liquid crystal layer region (B) is different fromboth the reference orientation directions c_(A) and c_(C) in the liquidcrystal layer regions (A) and (C) by 90°.

As described above, in this example, three different referenceorientation directions can be obtained in one liquid crystal cell. Thethree reference orientation directions are different from each other by90°, e.g., 9 o'clock, 12 o'clock, and 3 o'clock directions. Also asdescribed above, the substrates 1 and 11 are combined in such a mannerthat the boundary at which the aligning condition is changed on onesubstrate divides the portion which is not irradiated with ultravioletrays on the other substrate into two equal parts. Accordingly, it ispossible to obtain the liquid crystal layer regions (A), (B), and (C)which have substantially equal areas. Thus, the viewing characteristicsviewed in the directions, e.g., 9 o'clock, 12 o'clock, and 3 o'clock aremixed at the ratio of 1:1:1, so that good viewing performance can beobtained.

In this example, each of the liquid crystal layer regions (A), (B), and(C) corresponds to one pixel region. Alternatively, if one pixel regionis divided into sub-regions which correspond to the liquid crystal layerregions (A), (B), and (C), respectively, three different referenceorientation directions are formed in one pixel region. Accordingly, afiner image can be realized.

In the LCD of Example 2, the substrates are disposed in such a mannerthat the boundary between the different aligning conditions on onesubstrate side divides one aligning condition on the other substrateside, so that it is unnecessary to align the boundaries with each otherwhen the substrates are attached to each other and assembled into apanel. As a result, it is unnecessary to form a light blocking filmwhich was formed in view of the possible misalignment in the prior artrequiring the alignment of boundaries. Therefore, the reduction inopening ratio can be prevented.

EXAMPLE 3

In an LCD of Example 3, three types of liquid crystal layer regionshaving reference orientation directions which are different from eachother are formed, as in Example 2. In Example 2, the portions havingdifferent aligning conditions are formed on both sides of the basesubstrate i and the counter substrate 11. In Example 3, unlike Example2, only the aligning condition on the base substrate 1 side is varied inthree grades. FIG. 3A shows a cross section of the LCD of this example.Each of the liquid crystal layer regions (A), (B), and (C) correspondsto one pixel region.

A method for producing the LCD in this example is now briefly described.First, a transparent electrode 2 is formed on a base substrate 1. Then,a polyimide is applied onto the entire surface of the substrate so as tocover the transparent electrode 2, and then cured. The polyimide film isrubbed so as to obtain an alignment film 3. In this example, a polyimidefilm which provides a pretilt angle of 8° when it is not irradiated withultraviolet rays is used as the alignment film 3. Then, a 1/3 portion ofthe polyimide film is covered with a resist, and the remaining 2/3portion is irradiated with ultraviolet rays. In this irradiation, theintensity of ultraviolet rays is set to be 5-10 J/cm², whereby thepretilt angle δ of liquid crystal molecules which are in contact withthe irradiated portion is changed from 8° to 4°. Then, a half of theirradiated portion is covered with a resist. That is, the 2/3 portionincluding the portion which was previously covered is now covered withthe resists. The remaining 1/3 portion is irradiated with ultravioletrays having the intensity of 5-10 J/cm². Thus, the pretilt angle δ isfurther decreased. In this process, the 1/3 portions which are adjacentto each other are covered with the resists. In this example, the secondirradiation of ultraviolet rays results in the decrease of the pretiltangle δ of liquid crystal molecules from 4° to 1° or less.

Also, an alignment film 13 is formed on the counter substrate 11. UnlikeExample 2, the alignment film 13 is not irradiated with ultravioletrays. The alignment film 13 employed is a polyimide film which providesa pretilt angle which is equal to the middle one of the three grades ofpretilt angles which are realized by the alignment film 3 on the basesubstrate 1, when the polyimide film is not irradiated with ultravioletrays. In this example, as the alignment film 13, a material by which apretilt angle of 4° is obtained when it is not irradiated withultraviolet rays. Similarly to Examples 1 and 2, in this example, thepretilt angle δ is set to be smaller than 20°, and the differencebetween the pretilt angles on the base substrate 1 and the countersubstrate 11 is set to be equal to or larger than 1.5°.

Finally, the substrates 1 and 11 on which the alignment films are formedrespectively are combined so as to adapt the rubbing directions 3a and13a for the substrates 1 and 11 to the left-handed twisted liquidcrystal (see FIG. 3B). Into a gap between the combined substrates 1 and11, liquid crystal having right-handed twist property is injected. As aresult, a liquid crystal layer region (A) in which the pretilt angle onthe counter substrate 11 side is smaller than that on the base substrate1, a liquid crystal layer region (B) in which the pretilt angles in bothsubstrates are equal to 4°, and a liquid crystal layer region (C) inwhich the pretilt angle on the counter substrate 11 side is larger thanthat on the base substrate 1 side are formed.

FIG. 3B shows the relationship between the rubbing directions 3a and 13aon the alignment films 3 and 13 and reference orientation directions inthe respective liquid crystal layer regions. In the liquid crystal panelwhich is obtained in the above-described manner, the referenceorientation directions in the liquid crystal regions (A), (B), and (C)are set in the same manner as in Example 2. Specifically, in the liquidcrystal layer region (A), since the pretilt angle on the base substrate1 side is larger than that on the counter substrate 11 side, the liquidcrystal is right-handed twisted, and the in-plane orientation directionin the substrate (the reference orientation direction) of the liquidcrystal molecules in the vicinity of the center is the directionindicated by c_(A). In the liquid crystal layer region (B), thereference orientation direction is the direction indicated by c_(B). Inthe liquid crystal layer region (C), the reference orientation directionis the direction indicated by c_(C). It is preferred that the twistangles, the rubbing angles and the like of liquid crystal are set sothat the reference orientation direction c_(B) in the liquid crystallayer region (B) is different from both the reference orientationdirections c_(A) and c_(C) in the liquid crystal layer regions (A) and(C), respectively, by 90°.

In this example as well as Example 2, three different referenceorientation directions can be obtained in one liquid crystal panel. Asdescribed above, the liquid crystal layer regions are formed so as tohave equal areas, so the viewing characteristics viewed in the threereference viewing directions are mixed at the ratio of 1:1:1 and madeuniform, so that good viewing performance can be obtained. If one pixelregion is divided into a plurality of sub-regions which correspond tothe three types of liquid crystal layer regions, respectively, threedifferent reference orientation directions are formed in one pixelregion. Accordingly, a finer image can be realized.

In this example similar to Example 1, the aligning condition on thecounter substrate 11 side is set to be uniform, and the liquid crystallayer 4 is divided into three liquid crystal layer regions by boundariesbetween portions having different aligning conditions of the alignmentfilm 3 on the base substrate 1 side. Thus, it is unnecessary to alignthe boundary on the base substrate 1 side with the boundary on thecounter substrate 11 side when the substrates are attached to each otherand assembled into a panel. As a result, it is unnecessary to form ablack matrix which was formed in view of the possible misalignment inthe prior art. Therefore, the reduction in the opening ratio can beprevented.

EXAMPLE 4

In Example 4, in the LCD in Examples 2 and 3, the liquid crystal layerregion (B) in which the pretilt angle on the base substrate 1 side isequal to the pretilt angle on the counter substrate 11 side is providedat the boundary between the liquid crystal layer region (A) in which thepretilt angle on the base substrate 1 side is larger and the liquidcrystal layer region (C) in which the pretilt angle on the basesubstrate 1 side is smaller. The ratio in area of the liquid crystallayer region (B) in the substrate is set to be substantially 10% of thearea of the liquid crystal layer region (A) or (C) . The area of theliquid crystal layer region (B) is too small to contribute to theviewing characteristics of the liquid crystal panel. Due to such aconstruction, it is possible to substantially prevent the generation ofdisclination at the boundary between liquid crystal layer regions havingdifferent aligning conditions, which constitutes a problem when a Liquidcrystal layer region in which the pretilt angle on the base substrate 1side is larger is adjacent to a liquid crystal layer region in which thepretilt angle on the base substrate 1 side is smaller, so as to formreference orientation directions which are different from each other by180°.

In the above-described method in which the viewing performance isimproved by forming reference orientation directions different from eachother by 180° in one and the same panel, the disclination is generatedat the boundary between the liquid crystal layer regions havingdifferent reference orientation directions, which causes the contrast tobe degraded. However, in this example, in all portions at the boundarybetween liquid crystal layer regions having adjacent referenceorientation directions, liquid crystal molecules stand, so that thedisclination line is not observed. Therefore, even in the normally whitemode, it is not necessary to provide a light blocking film forsuppressing the light transmission due to the disclination. Thus, theopening ratio is not reduced, and hence a bright screen display can beobtained.

Next, a modification of Examples 1 to 4 will be described with referenceto FIG. 4. In the modification shown in FIG. 4, the alignment film 3 onthe base substrate i is partially irradiated with ultraviolet rays, sothat a chemical change occurs in the surface of the irradiated portion.As a result, a portion having a smaller pretilt angle than an inherentpretilt angle is formed. On the counter substrate 11, the alignment film13 is formed of a material having a pretilt angle which is smaller thanthe inherent pretilt angle of the alignment film 3 on the base substrate1 and is larger than the pretilt angle obtained as the result of theirradiation of ultraviolet rays. At this time, as in Example 1, thealignment film 13 on the counter substrate 11 is not irradiated withultraviolet rays. As the alignment film 3 on the base substrate 1, apolyimide film having a pretilt angle of 6° is used. The polyimide filmis covered with a photomask, and then irradiated with ultraviolet raysof 10 to 30 J/cm², so that the pretilt angle is set to be 1°or a smallerangle. For the alignment film 13 on the counter substrate 11, thepretilt angle is set to be 3°.

The substrates 1 and 11 having the above-described constructions areattached to each other so that the rubbing directions are adapted to theleft-hand twisted liquid crystal. Then, liquid crystal having theright-handed twist property is injected into a gap between thesubstrates 1 and 11. In this way, it is possible to obtain an LCD inwhich two grades of pretilt angles which are larger and smaller than thepretilt angle on the counter substrate 11 side are provided on the basesubstrate 1 side, while the aligning condition on the counter substrate11 side is entirely uniform. The reference orientation directions in thetwo liquid crystal layer regions having different pretilt angles on thebase substrate 1 side are different from each other by 180°. Therefore,the viewing characteristics in both the positive and negative viewingdirections are mixed and made uniform in the LCD shown in FIG. 4, sothat good viewing performance can be obtained. Each of the portionshaving different aligning conditions on the base substrate 1 side maycorrespond to one pixel region. Alternatively, portions having differentaligning conditions are formed in one pixel region. In the latterconstruction, a finer image can be obtained.

In the LCD shown in FIG. 4, the substrates are disposed in such a mannerthat the boundary between the different aligning conditions on onesubstrate side divides one aligning condition on the other substrateside, so that it is unnecessary to align the boundaries with each otherwhen the substrates are attached to each other and assembled into apanel, unlike the prior art. As a result, it is unnecessary to form ablack matrix which was formed in case of the possible misalignment.Therefore, the alignment of the substrates is the same as in the priorart, and the opening ratio is not reduced.

In cases where the partial aligning treatment cannot be performed on onesubstrate, a liquid crystal panel having superior viewingcharacteristics can be obtained according to the invention. This can be,for example, applied to the cases where a color filter is provided onthe substrate. In general, a color filter has a poor light resistance,and hence the color filter is not suitable for the division of thealigning conditions with light irradiation. In addition, since atransparent electrode (ITO) is formed on the color filter, it isdifficult to perform the patterning of the transparent electrode, andthe like. In such a case, if it is assumed that the LCD is of the activematrix type, a selective irradiation is performed on the TFT substrateside. Thus, a region having a larger pretilt angle (the inherent pretiltangle) and a region having a smaller pretilt angle as the result of theirradiation are formed. On the color filter substrate, an alignment filmhaving a pretilt angle which is smaller than the inherent pretilt angleof the TFT substrate side is formed. At this time, it is necessary toset the pretilt angle on the color filter substrate side larger than thesmaller pretilt angle on the TFT substrate side. When these substratesare combined, the reference orientation direction of liquid crystalbetween the substrates is regulated by the substrate with the largerpretilt angle. Accordingly, in the liquid crystal layer region in whichthe pretilt angle on the TFT substrate side is larger, the referenceorientation direction is regulated by the TFT substrate. In the liquidcrystal layer region in which the pretilt angle on the TFT substrateside is smaller, the orientation direction is regulated by the colorfilter substrate. As a result, reference orientation directionsdifferent from each other by 180° can be formed in the LCD. By usingthis method, the aligning dividing treatment is performed for only onesubstrate, so that the process can be simplified.

Next, another modification will be described with reference to FIG. 5.In the LCD shown in FIG. 5, the division of aligning conditions isperformed on both the alignment film 3 on the base substrate 1 and thealignment film 13 on the counter substrate 11. In this case, forexample, regions having different pretilt angles a, b, and c are formedon one substrate, and regions having different pretilt angles d and eare formed on the other substrate. Herein, the pretilt angles a to esatisfy the condition of a>d>b>e>c. When such substrates are combined, aunit liquid crystal layer region is divided into four regions, and twoorientation directions are alternately arranged. Therefore, it ispossible to obtain a finer image as compared with the case of the lightirradiation using a photomask.

In this modification, an even number of portions having differentpretilt angles are formed on the alignment film on one substrate side,and an odd number of portions having different pretilt angles are formedon the alignment film on the other substrate side. Specifically, asshown in FIG. 5, two portions having different pretilt angles are formedon the alignment film 3 on the base substrate 1 side, and three portionshaving different pretilt angles are formed on the alignment film 13 onthe counter substrate 11 side. In a method for forming three portionshaving different aligning conditions in the alignment film 13, asdescribed in Example 3, a 1/3 portion of the entire surface is firstcovered with a photomask. Then, the remaining 2/3 portion is irradiatedwith ultraviolet rays of 5 J/cm². Next, a half of the irradiated portionis covered with a photomask, i.e., the total 2/3 portion including theportion which is previously covered is covered with the photomask. Then,the remaining 1/3 portion is irradiated with ultraviolet rays of 5J/cm². As a result, a non-irradiated portion, an irradiated portion withultraviolet rays of 5 J/cm², and an irradiated portion with ultravioletrays of 10 J/cm² are obtained. In this modification, the employedalignment film 13 on the counter substrate 11 side is a polyimide filmhaving a pretilt angle of 9° without the irradiation of ultravioletrays. The polyimide film is subjected to the above-described process, sothat a portion having a pretilt angle of 9°, a portion having a pretiltangle of 5°, and a portion having a pretilt angle of 1° are formed.

In the alignment film 3 on the base substrate 1 side, a half of thesurface is covered with a photomask, and then the remaining portion isirradiated with ultraviolet rays. As a result, two portions havingdifferent aligning conditions are formed. As the alignment film 3 on thebase substrate 1 side, a material having a pretilt angle which has avalue between the largest pretilt angle and the second largest pretiltangle on the counter substrate 11 side, without the irradiation ofultraviolet rays. In this modification, a polyimide film having theinherent pretilt angle of 7° is used, and a half of the film isirradiated with ultraviolet rays of about 5 J/cm². As a result, thepretilt angle is set to be 3°.

Finally, the substrates 1 and 11 are combined in such a manner that therubbing directions are adapted to the left-handed twisted liquid crystaland the boundary between different aligning conditions on the basesubstrate 1 side divides the portion having the middle pretilt angle(herein, 5°) on the counter substrate 11 side. Then, liquid crystal withright-handed twist property is injected into a gap between thesubstrates 1 and 11. As a result, as shown in FIG. 5, four liquidcrystal layer regions (A), (B), (C), and (D) are obtained.

In the liquid crystal layer region (A), the pretilt angles on thecounter substrate 11 side and the base substrate 1 side are 9° and 7°,respectively. It is apparent that the pretilt angle on the countersubstrate 11 side is larger. In the liquid crystal layer region (C), thepretilt angles on the counter substrate 11 side and the base substrate 1side are 5° and 3°, respectively. It is apparent that the pretilt angleon the counter substrate 11 side is larger. Accordingly, in theseregions (A) and (C), the standing of the liquid crystal molecules in thevicinity of the center of the liquid crystal layer 4 is regulated by thealignment film 13 on the counter substrate 11. 0n the other hand, in theliquid crystal layer regions (B) and (D), the pretilt angle on the basesubstrate 1 side is larger. Thus, the standing of the liquid crystalmolecules in the vicinity of the center of the liquid crystal layer 4 isregulated by the alignment film 3 on the base substrate 1. Accordingly,reference orientation directions different from each other by 180° canbe alternately obtained in one and the same liquid crystal panel. Eachof such liquid crystal layer regions may correspond to one pixel region.Alternatively, one pixel region may be divided into a plurality ofsub-regions which correspond to the liquid crystal layer regions,respectively. In such a case, a finer image can be obtained.

In the LCD shown in FIG. 5, the pretilt angles on the substrate sidesare not limited to the above-described specific values. If the pretiltangles are selected so that they satisfy the above-defined relationshipin magnitude, and the difference between adjacent pretilt angles is 3°and the difference between opposing pretilt angles is 1.5°, a goodorientation control can be performed. If the pretilt angle exceeds 20°,the orientation regulation power in the entire liquid crystal cellbecomes stronger than the orientation regulation power of the alignmentfilm having the larger pretilt angle. Thus, it becomes impossible tocontrol the alignment of liquid crystal by the alignment film having thelarger pretilt angle. Therefore, it is necessary to set the maximumvalue of the pretilt angle to be 20° or less.

Alternatively, for example, one substrate has four aligning conditionsand pretilt angles of 10°, 7°, 4°, and 1°, and the other substrate hasthree aligning conditions and pretilt angles of 8.5°, 5.5°, and 2.5°.Alternatively, for example, one substrate has seven aligning conditionsand pretilt angles of 19°, 16°, 13°, 10°, 7°, 4°, and 1°, and the othersubstrate has six aligning conditions and pretilt angles of 17.5°,14.5°, 1.5°, 8.5°, 5.5°, and 2.5°. In this way, by dividing the aligningcondition into a larger number of aligning conditions, a finer image canbe obtained.

In the above-described example, the irradiation of ultraviolet rays isused for changing the aligning condition. It is assumed that the pretiltangle is changed by the irradiation of ultraviolet rays for thefollowing possible reasons.

If the polyimide film is supplied with a high energy by the irradiationof ultraviolet rays, the chemical structure of the surface of thepolyimide film is changed. More specifically, when the polyimide film isirradiated with ultraviolet rays, O₃ (ozone) is generated. The O₃oxidizes alkyl radicals of polyimide, so as to produce carbonylradicals. Due to the carbonyl radicals, the polarity of the surface ofthe polyimide film is changed, and the pretilt angle of liquid crystalmolecules which are polar molecules is also changed.

The surface tension of the polyimide film is changed by the irradiationof ultraviolet rays, so that the pretilt angle is changed.

In another mechanism, when the polyimide film is irradiated withultraviolet rays, the degree of roughness of the alignment film surfaceis changed. Such variation of degree of roughness of the alignment filmsurface is experimentally confirmed. It is also experimentally confirmedthat the pretilt angle is changed due to such variation.

EXAMPLE 5

In this example, the aligning conditions on each substrates are changedby a method other than the irradiation of ultraviolet rays. In thisexample, the alignment film surface in which a plurality of portionshaving different aligning conditions are to be formed is in contact with0.5% NaOH aqueous solution. By utilizing the non-uniform solubility ofthe solution to the alignment film, a desired degree of roughness isformed on the alignment film surface. Instead of the alkaline solutionsuch as an NaOH aqueous solution, it is possible to use an acidicsolution containing a hydrofluoric acid, a nitric acid or both of themas the main component. Alternatively, instead of such solutions, ifozone or ammonia gas, which is a reaction gas, is in contact with thealignment film surface, a desired degree of roughness is formed on thealignment film surface. Alternatively, if the surface of the alignmentfilm is subjected to a plasma treatment using a gas which is selectedfrom a group of oxygen (O₂), argon (Ar), krypton (Kr), and the like, itis possible to form the roughness on the alignment film surface.

As the result of the above-described process, various patterns ofdifferent aligning conditions may be obtained. For example, on each ofthe surfaces of the alignment films on the base substrate side and thecounter substrate side, two types of portions having different degreesof roughness are alternately formed by the above-described method. Thesubstrates are combined so as to align the boundaries between the twotypes of portions in such a manner that the portion which is highlyroughed on one substrate faces the portion which is not so roughed onthe other substrate. As a result, a liquid crystal layer region in whichthe pretilt angle on the counter substrate side is larger than that onthe base substrate and a liquid crystal layer region in which thepretilt angle on the counter substrate side is smaller than that on thebase substrate are alternately formed. Therefore, two types of regionshaving reference orientation directions which are different from eachother by 180° can be alternately formed in one and the same liquidcrystal panel.

Alternatively, for example, the surface of one alignment film ispartially roughed, so as to form two types of portions having differentaligning conditions. On one substrate, an alignment film having anintermediate degree of roughness between the two degrees of roughness onthe facing alignment film is formed. As a result, a liquid crystal layerregion in which the pretilt angle on one substrate is larger than thaton the other substrate and a liquid crystal layer region in which thepretilt angle on one substrate is smaller than that on the othersubstrate are formed in one and the same liquid crystal panel. Thelatter method has an advantage in that it is unnecessary to align theboundaries between the portions having different aligning conditionswhen the substrates are combined. At this time, each liquid crystallayer region may correspond to one pixel region. Alternatively, aplurality of such liquid crystal layer regions may be provided in onepixel region.

EXAMPLE 6

In Example 6, another method for forming roughness on the surface of thealignment film will be described. FIG. 6 simply shows a substrate 1 (11)in this example. Over the entire surface of the transparent substrate 1(11), a transparent conductive film 2 (12) is formed. Over the entiresurface of the transparent conductive film 2 (12), an alignment film 3(13) is formed. Example 6 is different from Example 5 in the followingpoint. In Example 5, the surface of the alignment film 3 (13) is roughedin a direct way. In Example 6, the roughness is formed on thetransparent conductive film 2 (12), and the alignment film 3 (13) isformed by printing thereon. Thus, the surface of the alignment film 3(13) is made rough.

The formation of the roughness on the surface of the transparentconductive film 2 (12) is performed by first forming the transparentconductive film 2 (12) on the transparent substrate 1 (11), and thenetching the surface of the transparent conductive film 2 (12) with anacidic solution or an alkaline solution. Alternatively, by performing aplasma treatment for the surface of the transparent conductive film 2(12) with a gas which is selected from a group of O₂, Ar, Kr, and thelike, the surface of the transparent conductive film 2 (12) can be maderough. Alternatively, the roughness may be formed by contacting areaction gas. On the transparent conductive film 2 (12) of which thesurface is roughed, the alignment film 3 (13) is formed by printing.Accordingly, the surface of the alignment film 3 (13) has the samedegree of roughness as that of the surface of the transparent conductivefilm 2 (12).

If a resist is used when the roughness is directly formed on the surfaceof the alignment film or when the condition of the alignment filmsurface is changed as in the above-described examples, there existproblems in that the surface of the alignment film is contaminated bythe resist, and the orientation regulating power of the alignment filmis degraded. However, in this example, the roughness is first formed onthe surface of the transparent conductive film 2 (12), and the roughnessis transferred to the surface of the alignment film 3 (13). Therefore,in this example, such problems of the contamination of the alignmentfilm surface by the resist and the degradation of orientation regulatingpower by the alignment film cannot occur.

In the method of Example 6 in which the roughness is formed on the film2 (12) which is disposed under the alignment film 3 (13) and theroughness is transferred to the surface of the alignment film 3 (13) soas to control the aligning characteristics, the underlying film may bemade of any material as far as the degree of roughness of the surface ofthe underlying film can be locally changed. Alternatively, a layerdisposed under the transparent conductive film 2 (12) may be subjectedto the surface treatment, and the roughness of the alignment film 3 (13)may be eventually controlled by the underlying layer.

The degree how the roughness of the surface of the transparentconductive film 2 (12) is transferred to the surface of the alignmentfilm 3 (13) can be controlled by the film thickness of the alignmentfilm 3 (13). That is, if the alignment film 3 (13) is thin, theroughness of the transparent conductive film 2 (12) is substantiallykept in the surface of the alignment film 3 (13). Thus, the surface ofthe alignment film 3 (13) may have substantially the same degree ofroughness as that of the transparent conductive film 2 (12). In the casewhere the alignment film 3 (13) is thick, even when the transparentconductive film 2 (12) has a higher degree of roughness, the degree ofroughness formed in the surface of the alignment film 3 (13) is lowerthan that in the transparent conductive film 2 (12). Therefore, byappropriately selecting the thickness of the alignment film 3 (13), adesired degree of roughness can be obtained. The thickness of thealignment film 3 (13) can be reduced, for example, by the irradiation ofultraviolet rays or by performing the development using photolithographyfor a longer time period than usual.

The portions having different degrees of roughness formed in the surfaceof the transparent conductive film 2 (12) may be formed in such apattern that each portion corresponds to one pixel portion.Alternatively, in one pixel region, a plurality of portions havingdifferent degrees of roughness may be formed. The variation pattern ofdegrees of roughness in the surface of the transparent conductive film 2(12) may be determined correspondingly to the pattern to be formed onthe surface of the alignment film 3 (13).

The thus obtained substrates 1 and 11 are attached to each other asdescribed in the above examples, and liquid crystal is injected into agap between the substrates 1 and 11. As a result, in one liquid crystalcell, a liquid crystal layer region in which the pretilt angle on thecounter substrate 11 side is larger than that on the base substrate iside, a liquid crystal layer region in which the pretilt angle on thecounter substrate 11 side is smaller than that on the base substrate 1side, and a liquid crystal layer region in which the pretilt angles onthe substrates 1 and 11 sides are equal to each other can be formed in adesired pattern so as to have desired areas, respectively. Therefore,according to this example, in one and the same liquid crystal cell, aplurality of reference orientation directions including referenceorientation directions which are different from each other by 180° canbe formed. As a result, superior viewing performance can be obtained.

EXAMPLE 7

In this example, similar to Example 6, the roughness is provided not onthe surface of the alignment film 3 (13) but on the surface of thetransparent conductive film 2 (12), and thus substantially the samedegree of roughness as in the transparent conductive film 2 (12) isprovided on the surface of the alignment film 3 (13). This example isdifferent from Example 6 in the following point. In this example, afterthe roughness is formed on the surface of the transparent conductivefilm 2 (12), an insulating film 43 is partially formed on thetransparent conductive film 2 (12). FIG. 7 simply shows a substrate ofthis example. As shown in FIG. 7, a transparent conductive film 2 (12)is formed over the entire surface of a transparent substrate 1 (11). Onthe transparent conductive film 2 (12), an insulating film 43 ispartially formed. Then, an alignment film 3 (13) is formed thereon overthe entire face of the substrate. As for the material of the insulatingfilm 43, silicon nitride, silicon oxide, or the like is used. In aportion of the surface of the alignment film 3 (13) corresponding to theedge of the insulating film 43, not only the surface condition of theinsulating film 43, but also the difference in level between the surfaceof the insulating film 43 and the transparent conductive film 2 (12)appear as large roughness. To the surface of the portion of thealignment film 3 (13) positioned above the surface of the insulatingfilm 43, the degree of roughness formed on the surface of thetransparent conductive film 2 (12) is not transferred. Thus, the surfaceof the portion of the alignment film 3 (13) positioned above the surfaceof the insulating film 43 has a condition depending on the surfacecondition of the insulating film 43.

In the above-described manner, in this example as well as in theabove-described examples, the surface of the alignment film 3 on thebase substrate 1 or the alignment film 13 on the counter substrate 11can be set to have desired aligning conditions. Then, the base substrate1 and the counter substrate 11 which are processed as described aboveare attached to each other, and liquid crystal is injected into a gapbetween the substrates 1 and 11. As a result, a liquid crystal layerregion in which the pretilt angle on the counter substrate 11 side islarger, a liquid crystal layer region in which the pretilt angle on thebase substrate 1 side is larger, and a liquid crystal layer region inwhich the pretilt angles on both substrate sides are equal to each otherare formed in a desired pattern so as to have desired areas,respectively. Therefore, in one and the same liquid crystal cell, aplurality of liquid crystal layer regions having different referenceorientation directions including the reference orientation directionswhich are different from each other by 180° can be formed. As a result,the viewing characteristics when viewed from a plurality of referenceorientation directions are mixed and made uniform, so that good viewingperformance can be obtained.

In this example, other processes such as the light irradiation for theformation of roughness or the formation of resists are not performedbefore the insulating film 43 is formed. In addition, the insulatingtreatment and the aligning control are performed in one process, so thatthe production process is very simplified. Thus, it is possible toprovide an LCD having superior viewing performance at a low cost.

EXAMPLE 8

Examples 8 to 10 describe exemplary cases for preventing thedeterioration in contrast due to a disclination line caused at theboundary between liquid crystal layer regions having referenceorientation directions different from each other which are formed in onepixel region.

FIG. 8 is a plan view showing one example in which the present inventionis applied to the TN mode active matrix type LCD. FIG. 9 is across-sectional view thereof. In the LCD, as is shown in FIG. 9, anactive matrix substrate 31 is disposed so as to face a counter substrate32, and a liquid crystal layer 33 is sealed therebetween. The activematrix substrate 31 includes an insulating substrate 31a made of glass.A plurality of scanning lines 12 and a plurality of signal lines 13 areformed so as to cross each other on the insulating substrate 31a. Ineach of the areas defined by the scanning lines 12 and the signal lines13, a pixel electrode 14 is disposed. In the vicinity of each of thecrossings of the scanning lines 12 and the signal lines 13, a thin filmtransistor 20 (hereinafter referred to as a TFT) as a nonlinear elementhaving a switching function is formed. The TFT 20 is electricallyconnected to one of the scanning lines 12, one of the signal lines 13,and the corresponding pixel electrode 14. The TFT 20 includes a gateelectrode 15 which is branched from the scanning line 12, a sourceelectrode 16 which is branched from the signal line 13 toward the pixelelectrode 14, and a drain electrode 17 of which the end overlaps thepixel electrode 14. As the TFT 20, an amorphous silicon TFT is employedin this example. The TFT 20 can be formed on the scanning line 12.

On the pixel electrode 14, there is superposed a scanning line 12 whichis adjacent to the scanning line 12 connected to the TFT 20 connected tothe pixel electrode 14. The superposed portion 18 functions as anadditional capacitance. In an alternative case, an additionalcapacitance line (not shown) is formed separately from the scanning line12. In such a case, the additional capacitance 18 can be formed on theadditional capacitance line.

Above these electrode lines, that is, above the scanning lines 12 andthe signal lines 13, and above the TFTs 20, an insulating protectivefilm 31d is formed in order to prevent short-circuits between thesubstrate 31a and these electrode lines and the TFTs and between theTFTs and the electrode lines. The insulating protective film 31d can beformed so as to have openings corresponding to respective pixelelectrodes 14.

In the counter substrate 32 which faces the active matrix substrate 31having the above-described structure, a color filter 32b, a counterelectrode 32c, and an alignment film 32e are formed in this order on aninsulating substrate 32a made of glass.

When the following process steps are performed for the LCD of thisexample having the above construction, the LCD which can actually bedriven to display can be produced. Specifically, the LCD which canactually be driven to display is produced by a step for formingalignment films 31e and 32e on the active matrix substrate 31 and thecounter substrate 32, respectively, a step for performing a rubbingtreatment for the alignment film 31e, a step for attaching the activematrix substrate 31 to the counter substrate 32, a step for providing aliquid crystal layer 33 by injecting liquid crystals between thesubstrates 31 and 32, and other steps, and then a step for mountingperipheral circuits such as a drive circuit.

In the production process, some process steps for providing a pluralityof liquid crystal layer regions having different reference orientationdirections in one pixel region are performed. In this example, in orderto allow two reference orientation directions to exist in one pixelregion, an aligning treatment is performed for the alignment film 31e ofthe active matrix substrate 31, so as to form a liquid crystal layerregion 19 having a reference orientation direction which is differentfrom the reference orientation direction in the other liquid crystallayer region over two or more pixel regions.

Such a liquid crystal layer region 19 is, for example, formed in thefollowing manner. A portion of at least one substrate corresponding toone liquid crystal layer region is covered with a protective film, andthe aligning treatment is performed in this state. Then, after theprotective film is removed, a portion corresponding to the other liquidcrystal layer region is covered with a protective film, and the aligningtreatment is performed so as to have a different aligning condition fromthat of the previously treated portion. In an alternative case, a regionof the surface of the pixel electrode 14 is chemically changed by usingliquid such as an acidic or alkaline solution, so as to make the surfacerough. Thus, the aligning directions are controlled by utilizing thedifference in tilt angles or tilt directions between the rough regionand the flat region. As a method for making the surface rough, thesurface may be chemically changed by gas, plasma, or by electromagneticwaves including light, or the surface may be physically changed bysolid, gas, plasma, or electromagnetic waves including light.

In the case where the insulating film is formed above the electrodelines and the TFTs, in order to prevent short-circuits between thesubstrates and between the electrode lines, the insulating film sur-face is treated so as to chemically change the surface condition byusing liquid such as an acidic or alkaline solution, gas, plasma, orelectromagnetic waves including light, or the like, or so as tophysically change the surface condition by using solid, gas, plasma,electromagnetic waves including light, or the like. Simultaneously, theinsulating film is patterned. As a result, the in-plane orientationdirections in the liquid crystal panel of the liquid crystal moleculesin the vicinity of the center of the liquid crystal layer along thethickness direction thereof, i.e., the reference orientation directionscan be controlled by controlling the tilt angles or the tilt directions.

Accordingly, in this example, in order to allow two referenceorientation directions to exist in one pixel region, a liquid crystallayer region having a reference orientation direction different fromthat of the other region is formed over two or more pixel regions.Accordingly, the boundary X of the liquid crystal layer regions withdifferent reference orientation directions is positioned over two ormore pixel regions. As a result, the free energy included in theboundary is reduced, so that the possibility of one aligning conditionbeing absorbed by the other aligning condition can be avoided. In thisway, the anisotropy of refractive indices of liquid crystal molecules isnot lost, and it is possible to ensure the optical rotatory power oflight. As a result, the viewing angle dependence of the contrast can beeliminated.

In this example, the aligning treatment for forming two liquid crystallayer regions having different reference orientation directions isperformed only for the alignment film 31e of the active matrix substrate31. For the alignment film 32e of the counter substrate 32, an aligningtreatment for applying a uniform aligning condition over the entiresurface thereof is performed. Alternatively, the aligning treatment forforming two types of liquid crystal layer regions having differentreference orientation directions may be performed only for the alignmentfilm 32e of the counter substrate 32, or for both the alignment films31e and 32e of the substrates 31 and 32. In such cases, it is possibleto eliminate the viewing angle dependence, similar to theabove-described case.

In this example, the boundary X between the liquid crystal layer regionswith different reference orientation directions is set so as to beparallel to the signal lines 13. However, this invention is not limitedto this specific setting. Alternatively, two types of liquid crystallayer regions may be formed so that the boundary X therebetween isparallel to the scanning lines 12, as is shown in FIG. 10. In such acase, it is possible to eliminate the viewing angle dependence for theabove-described reasons of the above examples.

In this example, in order to allow two reference orientation directionsto exist in one pixel region, two liquid crystal layer regions havingdifferent reference orientation directions are formed over two or morepixel regions. Again, this invention is not limited to this specificcase. Alternatively, in order to allow two, or three or more referenceorientation directions to exist in one pixel region, two, or three ormore liquid crystal layer regions having different reference orientationdirections may be formed over two or more pixel regions.

In addition, it is sufficient for the boundary between the liquidcrystal layer regions with different reference orientation directions toexist over two or more pixel regions. Accordingly, it is unnecessarythat the boundary continues over all the pixel regions in one column ofpicture elements among picture elements disposed in a matrix. In somecases, the boundary may be divided in one column.

EXAMPLE 9

Another example of the invention will be described.

FIG. 11 is a plan view showing an LCD of Example 9 of this invention.FIG. 12 is a cross-sectional view along the arrow A in FIG. 11. Likecomponents are indicated by like reference numerals to those in FIGS. 8and 9. In this LCD, unlike Example 8, two liquid crystal layer regionshaving different reference orientation directions are formed in eachpixel region. In FIG. 11, one of the two liquid crystal layer regionshaving different reference orientation directions is indicated by ahatched region, and the other region is indicated by a region withouthatching. In this example, on the alignment film 31e on the activematrix substrate 31 side, two types of portions having differentaligning conditions are formed in the above-described manner. As aresult, two types of liquid crystal layer regions having differentreference orientation directions are formed as shown in FIG. 11. At thistime, one of the portions having different aligning conditions of thealignment film 31e is rubbed so that the orientation direction of liquidcrystal molecules which are in contact with the portion coincides withthe direction B. These two types of liquid crystal layer regions arepositioned so that the boundary X therebetween is parallel to theorientation direction (the direction B) of the liquid crystal moleculeswhich are in contact with the alignment film 31e on the active matrixsubstrate 31 side. As the aligning treatment for forming liquid crystallayer regions having different reference orientation directions, thesame treatment as that performed in the above-described example can beperformed.

As described above, in this LCD, the boundary X between the two liquidcrystal layer regions with different orientation directions is parallelto the orientation direction (the direction B) of the liquid crystalmolecules which are in contact with the alignment film 31e of the activematrix substrate 31. Accordingly, the disorder of liquid crystalalignment can be suppressed, which results in the prevention of theabove-mentioned occurrence of the disclination line. In this example,liquid crystal layer regions having different reference orientationdirections disposed as shown in FIG. 11 are formed by performing thealigning treatment for forming two types of portions having differentaligning conditions for the alignment film 31e on the active matrixsubstrate 31 side. Alternatively, if such aligning treatment isperformed only for the alignment film 32e of the counter substrate 32,or for both the alignment films 31e and 32e of the substrates 31 and 32,the same effect as in this example can be attained. In the former case,it is necessary to set the boundary X between the liquid crystal layerregions to be parallel to the orientation direction of liquid crystalmolecules which are in contact with the alignment film 32e of thecounter substrate 32. In the latter case, the boundary X may be set soas to be parallel to the orientation direction of liquid crystalmolecules which are in contact with either the alignment film 31e of theactive matrix substrate 31 or the alignment film 32e of the countersubstrate 32.

As shown in FIG. 13, if the orientation direction (the direction B) ofliquid crystal molecules is different from that in the above-describedcase shown in FIG. 11, it is sufficient to form two liquid crystal layerregions with different reference orientation direction so that theboundary X therebetween is set to be parallel to the orientationdirection.

In the above cases, as is shown in FIGS. 11 and 13, two types of liquidcrystal layer regions having different reference orientation directionsare formed such that the boundary X therebetween is formed from one ofthe horizontally adjacent sides to the other side, or from one of thevertically adjacent sides to the other side of the display panel of theLCD. Again, the invention is not limited to these specific patterns. Theboundary X extending from one side does not necessarily reach the otherside. Alternatively, the boundary X may divide each of the two types ofliquid crystal layer regions having different reference orientationdirections.

In addition, in this example, the two types of liquid crystal layerregions with different reference orientation directions are formed ineach separate pixel region. Again, this invention is not limited to thisspecific case. Alternatively, as is shown in FIG. 14, a liquid crystallayer region 19 having a reference orientation direction which isdifferent from that of the other region may be formed over a pluralityof successive pixel regions. In such a case, in a portion of the pixelregion corresponding to the actual picture element, the boundary Xbetween the two liquid crystal layer regions with different referenceorientation directions should be set so as to be parallel to theorientation direction (the direction B) of the liquid crystal molecules.In other words, portions other than the picture element hardly affectthe orientation direction of liquid crystal molecules during thedisplay, so that the boundary X between the two liquid crystal layerregions is not necessarily parallel to the direction B. As the step offorming liquid crystal layer regions having different referenceorientation directions, the process described in each of theabove-described examples can be adopted.

Moreover, as shown in FIG. 13, in the case of the active matrix type LCDhaving the TFT 20 of a nonlinear element between the picture element andthe signal line, if the boundary X between the two liquid crystal layerregions with different reference orientation directions is positionedfarthest from the nonlinear element, it is possible to prevent thedeterioration of the nonlinear element during the treatment for makingthe surface rough, which is one of the process steps for formingportions having different aligning conditions in the alignment film.

In this example, it is appreciated that three or more liquid crystallayer regions with different reference orientation directions are formedin one pixel region, and the respective boundaries are set so as to beparallel to the orientation direction of liquid crystal molecules.

EXAMPLE 10

Next, still another example of the invention will be described.

In this example, two or more liquid crystal layer regions with differentreference orientation directions are formed, and a light blocking filmis formed on each boundary, so that light leaked from the boundaryportion is blocked by the light blocking film. In this case, it isunnecessary to set the boundary between the liquid crystal layer regionsto be parallel to the in-plane orientation direction of the liquidcrystal molecules which are in contact with one of the alignment films.

FIG. 15 is a plan view showing an LCD of this example, and FIG. 16 is across-sectional view thereof. In this LCD, the boundary between twoliquid crystal layer regions with different reference orientationdirections (one is indicated by the reference numeral 19) is coveredwith a light blocking film 21 which is extended from the drain electrode17.

Accordingly, in Example 10, the light leaked from the boundary portionin which any disclination line occurs can be blocked by the lightblocking film 21, so that the contrast can be enhanced. The lightblocking film 21 is formed of the same material as that of the drainelectrode 17 constituting the TFT 20 because the attaching accuracy ofthe two substrates is low. If the light blocking film 21 is separatelyformed, a positioning deviation occurs between the light blocking film21 and the TFT 20, both of which have the light blocking function, afterthe attachment of the substrates. As a result, the opening ratio isreduced. On the contrary, if the light blocking film 21 is formed of thesame material as the drain electrode 17, the deposition and etching forthe drain electrode 17 can be used for the formation of the lightblocking film 21. Thus, the number of process steps is not increased ascompared with the conventional process.

As shown in FIG. 16, the width D of the light blocking film 21 may beset to be a value with which the light blocking film 21 can block thelight leaked from the portion in which the disclination line occurs.

In this example, the light blocking film 21 is formed of the samematerial as that of the drain electrode 17. Alternatively, the lightblocking film 21 may be formed of the same material as any electrode orthe like having the light blocking function constituting the TFT 20. Insuch a case, the same effects can be attained.

The light blocking film 21 in this example can be formed so as to coverthe entire peripheral portions of the picture elements, as is shown inFIG. 17. Alternatively, the light blocking film 21 may be formed so asto cover the boundary X shown in Examples 8 and 9.

The techniques described in Examples 8, 9, and 10 can also be applied toany LCD of a desired mode and a desired structure, as well as to theLCDs of above-mentioned modes and structures.

As described above, according to the method for producing an LCD of thisinvention, the pretilt angles of liquid crystal molecules can be easilycontrolled. In addition, pretilt angles are changed for respectiveminute areas, so as to form different aligning conditions. Thesubstrates which are subjected to the aligning treatments are combined,so that a liquid crystal layer region in which different aligningconditions face each other and a liquid crystal layer region in whichequal aligning conditions face each other are mixedly formed. When thesubstrates are combined in such a manner that the pretilt angle on onesubstrate side is different from that on the other substrate side,reference orientation directions different from each other by 180° areformed. Another reference orientation direction which is perpendicularto these reference orientation directions is formed by combining thesubstrates in such a manner that the pretilt angle on one substrate sideis equal to that on the other substrate side. As a result, two or threereference orientation directions can be formed in one and the sameliquid crystal cell, and the viewing characteristics in two or threeviewing directions are mixed and made uniform. Between adjacent liquidcrystal layer regions having reference orientation directions differentfrom each other by 180°, a liquid crystal layer region in which thepretilt angle on one substrate side is equal to that on the othersubstrate side is formed. The liquid crystal layer region having equalpretilt angles on both sides has a smaller area than the adjacent liquidcrystal layer regions. As the result of the construction, there occursno discontinuity in liquid crystal at the boundary between differentaligning characteristics, so that a disclination line is not generated.

In the LCD of the invention, the boundary between different aligningconditions on one substrate is disposed so as to divide one aligningcondition on the other substrate. Thus, it is unnecessary to form ablack matrix at the boundary in view of the misalignment.

The LCD according to the invention which is produced as the result ofthe above-described aligning regulations can provide an image with highcontrast and high quality. According to the invention, the viewing angledependency of the LCD can be eliminated, and disadvantageous phenomenasuch as the phenomenon in which one aligning condition is absorbed byanother aligning condition as time elapses can be suppressed. Inaddition, a disclination line can be prevented from being generated atthe boundary between liquid crystal layer regions having differentreference orientation directions. Moreover, when a light blocking filmis formed, it is possible to prevent light (if any) from being leakedfrom a disclination line. Therefore, according to the invention, areliable LCD with improved display quality can be provided.

Various other modifications will be apparent to and can be readily madeby those skilled in the art without departing from the scope and spiritof this invention. Accordingly, it is not intended that the scope of theclaims appended hereto be limited to the description as set forthherein, but rather that the claims be broadly construed.

What is claimed is:
 1. A liquid crystal display apparatus comprising:afirst substrate and a second substrate disposed to face each other; aliquid crystal layer sandwiched between the first substrate and thesecond substrate; and a first alignment film formed between formedbetween the liquid crystal layer and the first substrate and a secondalignment film formed between the liquid crystal layer and the secondsubstrate; wherein the liquid crystal layer includes a plurality ofliquid crystal layer regions having aligning conditions which aredifferent from each other, optical transmittance of the plurality ofliquid crystal layer regions being variable to conduct display, theplurality of liquid crystal layer regions including a first liquidcrystal layer region and a second liquid crystal layer region, whereinan orientation direction in a substrate plane of liquid crystalmolecules in the vicinity of the center of the first liquid crystallayer region is different from an orientation direction in the substrateplane of liquid crystal molecules in the vicinity of the center of thesecond liquid crystal layer region, substantially by 90°, and wherein apretilt angle of the first alignment film is different from a pretiltangle of the second alignment film in the first liquid crystal layerregion, and a pretilt angle of the first alignment film is substantiallythe same as a pretilt angle of the second alignment film in the secondliquid crystal layer region.
 2. A liquid crystal display apparatusaccording to claim 1, wherein liquid crystal molecules in the secondliquid crystal layer region are twisted in a direction opposite to adirection in which liquid crystal molecules in the first liquid crystallayer region are twisted.
 3. A liquid crystal display apparatusaccording to claim 1, wherein a surface condition of the first alignmentfilm is different from a surface condition of the second alignment filmin the first liquid crystal layer region, and a surface condition of thefirst alignment film is substantially the same as a surface condition ofthe second alignment film in the second liquid crystal layer region. 4.A liquid crystal display apparatus according to claim 1, wherein asurface condition of the first alignment film in the first liquidcrystal layer region is substantially equal to a surface condition ofthe first alignment film in the second liquid crystal layer region, anda surface condition of the second alignment film in the first liquidcrystal layer region is different from a surface condition of the secondalignment film in the second liquid crystal layer region.
 5. A liquidcrystal display apparatus according to claim 4, wherein a pretilt angleof the first alignment film has an intermediate value between a pretiltangle of the second alignment film in the first liquid crystal layerregion and a pretilt angle of the second alignment film in the secondliquid crystal layer region.
 6. A liquid crystal display apparatusaccording to claim 1, wherein the plurality of liquid crystal layerregions further includes a third liquid crystal layer region, and anorientation direction in the substrate plane of liquid crystal moleculesin the vicinity of the center of the third liquid crystal layer regionis different from the orientation direction in the first liquid crystallayer region by 180°, and different from the orientation direction inthe second liquid crystal layer region by 90°.
 7. A liquid crystaldisplay apparatus according to claim 6, wherein a pretilt angle of thefirst alignment film and a pretilt angle of the second alignment film inthe third liquid crystal layer region are smaller than 20°, and adifference between the pretilt angles of the first and the secondalignment films in the third liquid crystal layer region is 1.5° ormore.
 8. A liquid crystal display apparatus according to claim 7,wherein the pretilt angle of the first alignment film is larger than thepretilt angle of the second alignment film in the first liquid crystallayer region, and the pretilt angle of the first alignment film issmaller than the pretilt angle of the second alignment film in the thirdliquid crystal layer region.
 9. A liquid crystal display apparatusaccording to claim 7, wherein the pretilt angle of the first alignmentfilm is smaller than the pretilt angle of the second alignment film inthe first liquid crystal layer region, and the pretilt angle of thefirst alignment film is larger than the pretilt angle of the secondalignment film in the third liquid crystal layer region.
 10. A liquidcrystal display apparatus according to claim 6, wherein the secondliquid crystal layer region is formed between the first liquid crystallayer region and the third liquid crystal layer region.
 11. A liquidcrystal display apparatus according to claim 10, wherein the first, thesecond, and the third liquid crystal layer regions have substantiallyequal areas.
 12. A liquid crystal display apparatus according to claim10, wherein an area of the second liquid crystal layer region is smallerthan an area of each of the first and the third liquid crystal layerregions.
 13. A liquid crystal display apparatus according to claim 6,wherein the first alignment film has equal surface conditions in all ofthe first, the second, and the third liquid crystal layer regions, andwherein the second alignment film has different surface conditions amongthe first, the second, and the third liquid crystal layer regions.
 14. Aliquid crystal display apparatus according to claim 6, wherein a surfacecondition of the first alignment film in the second liquid crystal layerregion is substantially equal to a surface condition of the firstalignment film in the first liquid crystal layer region, and a surfacecondition of the second alignment film in the second liquid crystallayer region is substantially equal to a surface condition of the secondalignment film in the third liquid crystal layer region.
 15. A liquidcrystal display apparatus according to claim 14, wherein pretilt anglesof the second alignment film in the first, the second, and the thirdliquid crystal layer regions are different from each other.
 16. A liquidcrystal display apparatus according to claim 1, wherein each of theplurality of liquid crystal layer regions corresponds to one pixelregion.
 17. A liquid crystal display apparatus according to claim 16,further comprising a light blocking film located on the boundary betweenthe plurality of liquid crystal layer regions.
 18. A liquid crystaldisplay apparatus according to claim 17, wherein a nonlinear element isformed in the pixel region, and the light blocking film is formed of anopaque material which constitutes the nonlinear element.
 19. A liquidcrystal display apparatus according to claim 1, wherein the plurality ofliquid crystal layer regions are formed in one pixel region.
 20. Aliquid crystal display apparatus according to claim 19, wherein anonlinear element is formed in the pixel region, and the nonlinearelement is positioned as far as possible from the boundary between theplurality of liquid crystal layer regions.
 21. A liquid crystal displayapparatus according to claim 19, wherein an orientation direction in thesubstrate plane of liquid crystal molecules which are in contact withone of the first alignment film and the second alignment film issubstantially parallel to a boundary between the plurality of liquidcrystal layer regions.
 22. A liquid crystal display apparatus accordingto claim 1, wherein each of the plurality of liquid crystal layerregions are continuously formed over a plurality of pixel regions.
 23. Aliquid crystal display apparatus according to claim 22, wherein anorientation direction in the substrate plane of liquid crystal moleculeswhich are in contact with one of the first alignment film and the secondalignment film is substantially parallel to a boundary between theplurality of liquid crystal layer regions.
 24. A liquid crystal displayapparatus according to claim 22, wherein a nonlinear element is formedin the pixel region, and the nonlinear element is positioned as far aspossible from the boundary between the plurality of liquid crystal layerregions.
 25. A liquid crystal display apparatus according to claim 1,wherein the pretilt angle of the first alignment film and the pretiltangle of the second alignment film in the first liquid crystal layerregion are smaller than 20°, and a difference between the pretilt anglesof the first and second alignment films in the first liquid crystallayer region is 1.5° or more.
 26. A method for producing a liquidcrystal display apparatus comprising a first substrate and a secondsubstrate disposed to face each other and liquid crystal sandwichedbetween the first substrate and the second substrate, the methodcomprising:a step of forming a first alignment film on the firstsubstrate, and forming a second alignment film on the second substrate;a surface treatment step of forming a plurality of portions havingsurface conditions which are different from each other, on at least oneof the first alignment film and the second alignment film; and anassembly step of attaching the first substrate to the second substrate,and injecting the liquid crystal between a first substrate and thesecond substrate, so as to form a plurality of liquid crystal layerregions having different orientation directions in a substrate plane ofliquid crystal molecules in the vicinity of the center of the liquidcrystal along a thickness direction of the liquid crystal between thefirst and the second substrates, the plurality of liquid crystal layerregions having variable optical transmittance to conduct display,wherein the plurality of liquid crystal layer regions includes a firstliquid crystal layer region and a second liquid crystal layer region; anorientation direction in the substrate plane of liquid crystal moleculesin the vicinity of the center of the first liquid crystal layer regionis different from an orientation direction in the substrate plane ofliquid crystal molecules in the vicinity of a center of the secondliquid crystal layer region substantially by 90°; and a pretilt angle ofthe first alignment film is different from a pretilt angle of the secondalignment film in the first liquid crystal layer region, and a pretiltangle of the first alignment film is substantially the same as a pretiltangle of the second alignment film in the second liquid crystal layerregion.
 27. A method for producing a liquid crystal display apparatusaccording to claim 26, wherein the plurality of liquid crystal layerregions further includes a third liquid crystal layer region, and anorientation direction in the substrate plane of liquid crystal moleculesin the vicinity of the center of the third liquid crystal layer regionis different from the orientation direction in the first liquid crystallayer region substantially by 180°, and different from the orientationdirection in the second liquid crystal layer region substantially by90°.
 28. A method for producing a liquid crystal display apparatusaccording to claim 27, wherein the first alignment film includes a firstand a second portions having different pretilt angles, and the secondalignment film includes a third and a fourth portions having differentpretilt angles, and wherein the method further includes a step ofpositioning the first and the second substrates so that the secondportion of the first alignment film is divided by a boundary between thethird and the fourth portions of the second alignment film.
 29. A methodfor producing a liquid crystal display apparatus according to claim 26,wherein the surface treatment step includes a step of forming aplurality of portions having different pretilt angles by partiallychanging the surface condition of at least one of the first and thesecond alignment films.
 30. A method for producing a liquid crystaldisplay apparatus according to claim 29, wherein the step of forming theplurality of portions having different pretilt angles includes a step ofbringing the at least one of the first and the second alignment filmsinto contact with one of an acid solution, an alkaline solution, andsolutions containing these as main components.
 31. A method forproducing a liquid crystal display apparatus according to claim 29,wherein the step of forming the plurality of portions having differentpretilt angles includes a step of irradiating the at least one of thefirst and the second alignment films with a plasma of a gas selectedfrom a group consisting of O₂, Ar, and Kr.
 32. A method for producing aliquid crystal display apparatus according to claim 29, furthercomprising a step of forming an underlying film on each of the first andthe second substrates, prior to the step of forming the first and thesecond alignment films, wherein the surface treatment step includes astep of making a part of at least one of the underlying films havingdifferent degrees of roughness, and a step of forming the first and thesecond alignment films on the underlying films, thereby changing asurface condition of at least one of the first and the second alignmentfilms.
 33. A method for producing a liquid crystal display apparatusaccording to claim 32, wherein the step of making different degrees ofroughness includes a step of selectively irradiating the underlying filmwith ultraviolet rays.
 34. A method for producing a liquid crystaldisplay apparatus according to claim 32, wherein the step of makingdifferent degrees of roughness includes a step of bringing theunderlying film into contact with one of an acid solution, an alkalinesolution, and solutions containing these as main components.
 35. Amethod for producing a liquid crystal display apparatus according toclaim 32, wherein the step of making different degrees or roughnessincludes a step of irradiating the underlying film with a plasma of agas selected from a group consisting of O₂, Ar, and Kr.
 36. A method forproducing a liquid crystal display apparatus according to claim 32,wherein the step of making different degrees of roughness includes astep of forming an insulating film on a predetermined area of a surfaceof the underlying film.
 37. A method for producing a liquid crystaldisplay apparatus according to claim 32, wherein the step of makingdifferent degrees of roughness includes a step of forming the differentdegrees of roughness in at least one of the underlying films byphotolithography.
 38. A method for producing a liquid crystal displayapparatus according to claim 32, wherein, in the step of forming thefirst and the second alignment films on the underlying films, a surfacecondition of at least one of the first and the second alignment films iscontrolled by changing a thickness of the at least one of the first andthe second alignment films.
 39. A method for producing a liquid crystaldisplay apparatus according to claim 29, wherein the step of forming theplurality of portions having different pretilt angles includes a step ofselectively irradiating the at least one of the first and the secondalignment films with ultraviolet rays.
 40. A method for producing aliquid crystal display apparatus according to claim 26, wherein in theassembly step, the first and the second substrates are assembled so asto adapt to liquid crystal having a twisted property in a directionopposite to a direction in which the injected liquid crystal is twisted,whereby the twisted directions in the plurality of liquid crystal layerregions are different from each other.